Early seat and backrest cushioning was made from down and fabric materials (e.g., polyester fiber or cotton) which offered great comfort, but offered little support especially as these materials compacted with use.
Although the introduction of latex foam rubber offered increased durability and support for seat and backrest cushioning, it was eventually overshadowed by a more cost-effective flexible polyurethane foam (FPF). Flexible polyurethane foam greatly enhanced the comfort level in most seating applications. However, even high density, High Resilience (HR) polyurethane foam lacked the support necessary for reducing spinal strain, circulatory inhibition and pressure ulcers, which are especially prevalent among persons confined to sitting for a prolonged period of time.
Visco elastic foam (“memory foam”) is an open-celled, body-heat and body-weight sensitive material originally developed by NASA to alleviate the G-Force stresses and pressures placed on astronauts during space flight. Memory foam material automatically conforms to the shape and position of the body and returns to its original shape and re-conforms with a change in body position. However, memory foam lacks the lateral support necessary for optimal pelvic positioning and improved postural alignment required for increased sitting comfort and sitting tolerance.
As such, there is a need for a seat and backrest that is comfortable, durable and which provides support. The seat and backrest should be comfortable for both short and long term sitting. The seat and backrest also should be durable to withstand different pressures from different body weights over a period of time and should also provide enough support to prevent or alleviate human ailments (e.g., spinal strain, thrombosis or pressure ulcers) acquired or aggravated by sitting.